Barbey P., Denele Y., Paquette J. L., Berger J., Ganne Jérôme, Roques D. (2018). The Marbat metamorphic core-complex (Southern Arabian Peninsula) : reassessment of the evolution of a Neoproterozoic island-arc from petrological, geochemical and U-Pb zircon data. Precambrian Research, 305, p. 91-110. ISSN 0301-9268.
Titre du document
The Marbat metamorphic core-complex (Southern Arabian Peninsula) : reassessment of the evolution of a Neoproterozoic island-arc from petrological, geochemical and U-Pb zircon data
Barbey P., Denele Y., Paquette J. L., Berger J., Ganne Jérôme, Roques D.
Source
Precambrian Research, 2018,
305, p. 91-110 ISSN 0301-9268
The Marbat basement (Sultanate of Oman) belongs to the Neoproterozoic accretion domain of the Arabian-Nubian shield. We present new geochronological, petrological and geochemical data as an extension of our previous study (Denele et al., 2017) re-interpreting this basement as a metamorphic core complex (MCC). We showed that this MCC consists of a metamorphic unit (Juffa complex) separated by an extensional detachment from a plutonic unit (Sadh complex and Tonalite plutons). Geochemical data show that the Juffa metasediments correspond to volcanogenic graywackes, suggesting deposition in front of a juvenile magmatic arc. New in situ U-Pb zircon data show that the protolith of the Juffa paragneisses is Tonian in age (960-830 Ma). The Juffa complex recrystallized under amphibolite facies conditions (950 MPa, 630 degrees C) corresponding to thermal gradient of 17-18 degrees C/km, i.e. close to that observed in fore-arc environment subjected to tectonic underplating. It was then retrogressed (< 400 MPa, < 400 degrees C) during exhumation of the MCC. Phase assemblages of the Sadh complex and Tonalite plutons record magmatic temperatures estimated at 700-840 degrees C and 610-840 degrees C from hornblende and zircon-saturation thermometry, respectively; pressures are grossly estimated at ca. 250 MPa. These data and structural evidence led us to consider that the Sadh complex is a plutonic unit emplaced during exhumation of the MCC. Hence, we re-interpret the previously published zircon core U-Pb ages of the Banded gneisses (ca. 860-830 Ma) as inherited, and zircon rim ages (ca. 815 Ma) as the age of their intrusion. This suggests that the parent magma of all these granitoids could have interacted with volcanic material equivalent to the Juffa complex. Overall, the Marbat area developed during the Tonian and involved (i) deposition of volcanosediments (Juffa complex) in an island-arc environment (960-830 Ma); (ii) metamorphism under middle pressure conditions during tectonic underplating at ca. 820-815 Ma, followed by emplacement of plutonic rocks in the upper crust during initiation of the MCC at ca. 815-810 Ma; and (iii) late-tectonic intrusions associated with MCC amplification at ca. 800-790 Ma (Mahall intrusives and Tonalite plutons).
Plan de classement
Géologie et formations superficielles [064]
;
Géophysique interne [066]
